Impact
A major blind SSRF has been found in remark-images-download, which allowed
for requests to be made to neighboring servers on local IP ranges.
The issue came from a loose filtering of URLs inside the module.
Imagine a server running on a private network 192.168.1.0/24.
A private service serving images is running on 192.168.1.2, and
is not expected to be accessed by users. A machine is running
remark-images-download on the neighboring 192.168.1.3 host.
An user enters the following Markdown:
The image is downloaded by the server and included inside the resulting
document. Hence, the user has access to the private image.
It has been corrected by preventing images downloads from
local IP ranges, both in IPv4 and IPv6.
To avoid malicious domain names, resolved local IPs from are also
forbidden inside the module.
This vulnerability impact is moderate, as it is can allow access to
unexposed documents on the local network, and is very easy
to exploit.
Patches
The vulnerability has been patched in version 3.1.0.
If impacted, you should update to this version as soon as possible.
Please note that a minor version has been released instead of a bugfix.
This is due to a new option included to prevent another vulnerability,
upgrading to the new version will not break compatibility.
Workarounds
No workaround is known, the package should be upgraded.
For more information
If you have any questions or comments about this advisory, open an issue in ZMarkdown.
References
gustavi Finder
Impact
A major blind SSRF has been found in
remark-images-download, which allowedfor requests to be made to neighboring servers on local IP ranges.
The issue came from a loose filtering of URLs inside the module.
Imagine a server running on a private network
192.168.1.0/24.A private service serving images is running on
192.168.1.2, andis not expected to be accessed by users. A machine is running
remark-images-downloadon the neighboring192.168.1.3host.An user enters the following Markdown:
The image is downloaded by the server and included inside the resulting
document. Hence, the user has access to the private image.
It has been corrected by preventing images downloads from
local IP ranges, both in IPv4 and IPv6.
To avoid malicious domain names, resolved local IPs from are also
forbidden inside the module.
This vulnerability impact is moderate, as it is can allow access to
unexposed documents on the local network, and is very easy
to exploit.
Patches
The vulnerability has been patched in version 3.1.0.
If impacted, you should update to this version as soon as possible.
Please note that a minor version has been released instead of a bugfix.
This is due to a new option included to prevent another vulnerability,
upgrading to the new version will not break compatibility.
Workarounds
No workaround is known, the package should be upgraded.
For more information
If you have any questions or comments about this advisory, open an issue in ZMarkdown.
References